Programming of memory cells can be accomplished by changing the phase of materials, i.e., from amorphous to crystalline state. The publication entitled “OUM—A 180 nm Nonvolatile Memory Cell Element Technology For Stand Alone and Embedded Applications” by Stefan Lai, et al., Intel Corp., Santa Clara, Calif., February 2001, Proceedings of: Electron Devices Meeting, 2001, IEDM Technical Digest International, IEEE Xplore (2001), herein incorporated by reference, discusses the development status of the memory cell element of OUM (Ovonic Unified Memory)—a chalcogenide based, phase-change nonvolatile, semiconductor memory technology involving phase changing materials. OUM is a nonvolatile memory that utilizes a reversible structural phase change between amorphous and polycrystalline states in a GeSbTe chalcogenide alloy material. Because of the very small size, temperature steps required to form the elements do not compromise transistor performance. During the amorphizing reset pulse, the temperature of the programmed volume of phase-change material exceeds the melting point which eliminates the polycrystalline order in the material. The crystallizing set pulse is of lower amplitude and sufficient duration (12-50 ns) to maintain device temperature in the rapid crystallization range for a time sufficient for crystal growth.
The publication entitled “A GeSbTe Phase-Change Memory Cell Featuring a Tungsten Heater Electrode for Low-Power, Highly Stable, and Short-Read-Cycle Operations” by N. Takaura, et al, International Electron Devices Meeting; IEEE, 897-900 (2003) ISBN 0780378725) (herein incorporated by reference, features a Germanium-Antimony-Tellurium (GeSbTe) memory cell with a tungsten heater electrode. The cell has a reset current (50/spl mu/A) for the phase-change memory device.